The first person to have predicted that emissions of carbon
dioxide from the burning of fossil fuels would cause a global
warming is considered to be S.Arrhenius, who published in
1896 the paper 'On the influence of carbonic acid in the air
upon the temperature of the ground'.

That atmospheric carbon dioxide was actually increasing was
confirmed beginning in the 1930s, and convincingly beginning
in the 1950 s when highly accurate measurement techniques
were developed (the most famous demonstration of this is in
C.D.Keeling's record at Mauna Loa, Hawaii). By the 1990s, it
was widely accepted (but not unanimously so) that the Earth's
surface air temperature had warmed over the past century.
An ongoing debate is whether such a warming can, in fact, be
attributed to increasing carbon dioxide in the atmosphere.